I saw your workstation pic in the gallery thread, you have a micro ATX case, correct? The 9800GTX is 10.5" long, there is very little chance that it will fit.
Just go with the 9800GT
, it's more than enough for 1280x1024, it's cheaper, it's only 9" long, and YES, you will be able to play Crysis Warhead. I just finished that game BTW, it was one of the worst games I've ever played in my life, especially the cut scenes.